Process for the production of chlorinated rubber



Patented Nov, 5,1935

PATENT OFFICE ammo PROCESS FOR THE PRODUCTION OF OHLOBINA'I'ED RUBBER Eugen'liliillney, Ammendorf, Germany, assignmto the firm Chemische Fabrik Buckau, .Am-

Germany -memlorf (Saalhreis).

No Application May zz, 1934, Serial No. 120,954. In Germany May 26,193:

a cum. (01. 134-11) This invention relates to a process for the production of chlorinated rubber.

Chlorinated rubber is usually produced by passing chlorine through solutions of raw rubber.

However, both the originating solutions and the resulting solutions ofchlorinated rubber are usually very highly viscous liquids and are consequently very difllcult to manipulate. 'Attempts have already been made to lower the high viscosity of these'liquids, either by heating them, lessening, their rubber content, or finally, by irradiation, especially with ultravioletrays.

These measures however, areattended with certain difilculties so that for, example, notwithstanding the employment of high temperatures,

stirring devices are always required to keep the liquids in continuous movement and if it be desired to lower the viscosity by operating with low rubber concentrations, comparatively large quantities of liquid have to be passed through the ap-' paratus, thereby rendering the whole process more expensive. The irradiation of the solutions entails the construction of a special apparatus, which may not be of a simple character, and the inclusion of which in the process gives rise to special diiliculties.

The present invention aims at obviating these difficulties. To this end,. the invention consists in adding hypochlorites to the solutions used in the process of producing chlorinated rubber. Such hypochlorites may be added before, during or after chlorination, or also during several or all of the stages of the process; nevertheless, it

is preferable to add the hypochlorite to the solu-' tions of raw rubber prior tochlorination.

The hypochlorites employed may be those of the alkali metals including ammonium in this term or also those of the alkaline earth metals.

When small quantities of such a hypochlorite are added to a freshly prepared rubber solution, which is highly viscous, and the solution-is stirred a liquid is obtained within a comparatively short time, which is of such low viscosity that it can be chlorinated to form chlorinated rubber in a;

- diminishes to' 1 second after the solution has been stirred for half' an hour;

' If, alsdby way of example, a 4% solution of rubber in carbon tetrachloride is treated with ,3 of potassium hypochlorite solution, containing 160 grms. of active chlorine per litre, the 1 original viscosity which is too high to be measured, falls to!) seconds after an hour's stirring.

The best results are obtained when the amount 5 of hypochlorite added does not exceed that cor- Y responding to a content of 1% of active chlorine referred to the solution of rubber or of chlorinated rubber;

- The low-viscositysolutions obtained in this manner can now be very easily further treated without the aforesaid difficulties being encountered.

As already mentioned, it is unnecessary to confine the additionof the hypochlorites to the origll6 nal rubber solution, but it has also been found highly useful to add a certain small quantity of ,hypochlorite during chlorination especially towardsthe end of that operation. By this means the precipitation of incompletely chlorinated rubber which sometimes occurs is avoided Fi- )rubber will at once exhibit a fine white colour which could-hitherto be obtained only by prolonged storage or irradiation of the solution.

What I-claim is:

'1. In the production of rubber chloride solu- 80 tions by the chlorination of rubber solutions, the process which comprises adding to such a solution prior to the final precipitation of the resulting rubber chloride 9. small amount-of a hypochlorite selected from a group consisting of the alkali metal and alkaline earth metal hypochlorites.

2. The process of reducing the viscosity and improving ,the quality of rubber chloride solutions resulting from the chlorination of a rubber solution which comprises adding to at least one of said solutions prior to precipitation of the rubber chloride a small amount of a hypochlorite selected from a group consisting of the alkali metal and alkaline earth metal hypochlorites.

.3. The process of claim 2 wherein the hypo- 'chlorite is added to the rubber solution chlorination. g l

4'. The process of claim 2 wherein the hypochlorite is added to the solutiondurlng chlorina- '9 ..tion.

' 5. of 2 wherein the hypochlorite is added to the solution after chlorination.

c. The process of claim 2fwhereina hvpochlou rite is added to the solution at more than one stage of its process of chlorination.

7. The process of claim 2 wherein the amount of hypochlorite added does not substantially exceed an amount corresponding to 1 per cent calculated as active chlorine, based on the solution of rubber or of chlorinated rubber. v

8. The process of claim 2 wherein the hypo-- chlorite is potassium hypochlorite.

9. The process of claim 2 wherein the hypochlorite is sodium hypochlorlte.

EUGEN MGLLNEY. 

